blog:286_shootout_vlsi_vl82c311l

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blog:286_shootout_vlsi_vl82c311l [2021/03/13 14:14] – [Motherboard Data & Variants] johnblog:286_shootout_vlsi_vl82c311l [2021/04/23 14:09] (current) – [Further Testing] john
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 Next I'll need to remove the keyboard socket and repair those battery terminal tabs and any other corrosion around the area (which isn't a lot). Next I'll need to remove the keyboard socket and repair those battery terminal tabs and any other corrosion around the area (which isn't a lot).
 +
 +//Below:// Keyboard socket replaced and battery tab solder points re-filled:
 +
 +{{:blog:286:img20210313125205.jpg?500|}}
 +
 +//Below:// DIL-14 sockets fitted in place of the original oscillator solder pads and 40MHz and 32MHz cans pushed in:
 +
 +{{:blog:286:img20210313203159.jpg?500|}} {{:blog:286:img20210313212205.jpg?500|}}
 +
 +So, did it work?
 +
 +Well.....
 +
 +{{:blog:286:img20210313211347.jpg?500|}}
 +
 +The POST diagnostic card indicates reset held high and no CLK signal :-(
 +
 +**[Update 14/03/2021]** - I swapped the processor on a chance it was faulty... 
 +
 +{{:blog:286:img20210314123150.jpg?500|}}
 +
 +The held reset light now goes out, and the CLK light stays lit. So that's an improvement. Still no error codes though.
 +
 +==== Further Testing ====
 +
 +=== Clock Signals ===
 +
 +The 14MHz oscillator which was still fitted to the board on receiving it is working; the clock is present on the output pin from the can as well as on ISA socket pin B30 (//OSC//):
 +
 +{{:blog:286:20210423_133918.png?600|}}
 +
 +There is an 8MHz clock present on ISA socket pin B20 (//CLK//):
 +
 +{{:blog:286:20210423_134011.png?600|}}
 +
 +Processor pin 31 (//CLK//) has a 9.996MHz clock:
 +
 +{{:blog:286:20210423_135456.png?600|}}
 +
 +//This doesn't seem correct//. The processor is a 20MHz unit, and is being driven, as is normal on a 286, by a standard DIL can oscillator of 2x the processor frequency (i.e. 40MHz). The definition for pin 31 is that it //"is divided by 2 internally within the processor to generate the processor clock"// (from the {{ :blog:286:amd_80286_datasheet_june_1989_.pdf|AMD 80286 datasheet}})... that would mean the processor is only at 5MHz. Unless I misunderstand the datasheet, something is drastically wrong here.
 ===== Configuration ===== ===== Configuration =====
  
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  • Last modified: 2021/03/13 14:14
  • by john